Hi Eric,
R U talking about De Winton locos?
They had a wheelbase of 4ft or 4ft6ins, on 2ft Gauge slate quarry tracks. I dont think much change was made to the basic design regardless of track gauge – some were 3ft. DW probably most prolific builder of type. I think most other builders made only a one-off or perhaps 2.
Rgds,
John.